How much heat is needed to raise the temperature of 90g of water by 64oC?

The heat released or absorbed by a process where temperature changes is calculated from the product of the mass of the sample, its heat capacity (4.18 J/g C for water) and the change of the temperature.

Heat = mC (T)

Heat = 90 (4.8) (64) = 27648 J or 27.65 kJ needed